A Light and Electron Microscopic Study on Epitheliocystis Disease in Cultured Fishes

Abstract

Epitheliocystis disease was found in red sea bream Pagrus major, transported from Hong-Kong, and tiger puffer Takifugu rubripes and carp Cyprinus carpio cultured in Japan. Histopathological and electron microscopic studies were made on these diseased fishes. Epitheliocystis cysts of these fishes developed in gills. Cysts of red sea bream were found on the capillary under respiratory epithelium of gill lamellae in the early stage of the infection. Heavily infected gills showed many cysts among the hyperplastic epithelium of the interlamellar spaces, followed by clubbing of the gill filaments. The cysts ranged in diameter from 15 μm to 55 μm. The cysts had a cellular capsule and an inclusion body which was revealed to be packed with chlamydia-like organisms ranging from 0.52 pm to 0.71 pm in size, by electron microscopy. Epitheliocystis cysts of tiger puffer developed on the capillary under the respiratory epithelium of gill lamellae. The cysts ranged in size from 25 pm to 43 pm. Epitheliocystis cysts of red sea bream and tiger puffer indicated that they developed from infected cells forming lamellar capillaries. Epitheliocystis cysts of carp developed within the epithelium of the interlamellar spaces on gill filaments and ranged in diameter from 12 μm to 50 μm. © 1986, The Japanese Society of Fisheries Science. All rights reserved.